On principles of analysis of Russian prepositional units

The article introduces several formal operational methods of differentiation of prepositions and words that are able to perform the functions of prepositions in certain contexts but are not considered ones. It is possible to make a formal distinction between prepositions proper and their equivalents on the basis of these characteristics. This is the first opposition in the system of morphological-syntactic types of prepositional units, revealing the multitudes of ‘prepositions proper’ and ‘preposition equivalents’.